Step 1: See if the smaller denominator divides into the
larger denominator with no remainder.
Say we want to add:
Because 9/3 = 3, the lowest common denominator is 9. After that we
because 3/3 = 1. Then we replace 1/3 by 3/9 in the problem.
Step 2: If step 1 doesn't work, we use the Euclidean Algorithm
to first find the largest divisor of both numbers. Say we add:
using the Euclidean Algorithm, we find that 3 is the largest divisor of 12 and
9. We then follow these steps:
1. Divide the first denominator by 3.
2. Multiple the second fraction by 4/4 because 4 was the answer from
3. Divide the second denominator by 3.
4. Multiple the first fraction by 3/3 because 3 was the answer from
the second division.
5. Add the two fractions with the common denominator.